- Characterization of the human and mouse HEY1, HEY2, and HEYL genes: cloning, mapping, and mutation screening of a new bHLH gene family. Steidl, C., Leimeister, C., Klamt, B., Maier, M., Nanda, I., Dixon, M., Clarke, R., Schmid, M., Gessler, M. Genomics (2000)